Cap for electric-light sockets



a UNITED STATES PATENT OFFICE.

AJEXANDEB w. LmoNT, 01 BRIDGEPORT e muss COMPANY, or* temnearom,

* NECTICUT.

Specfication of Letters Patent.,

, CONNCTICUT, ASSIGNOR To BRIDGEI'ORT CONNECTICU'E, A CORPORATION OF CON CAP FOR ELECTBIG-LIGT SOCKETS.

* Patented Nov. 15,1921.

'original application filed February 10, 1915, Serial No. 7,291. Dlvided and this application filed August 26, 1915.

To all 'whom 'it may] camera: l

Be it known that I, ALEXANDER W. L1-

i MONT,a citizen of theUnited States, residing in a Bridgeport, county of Fairfield, and State of Connecticut, have invented certain new and useful Improvements in aps for Electric-Liht Sockets, of which the following 'is a fu l, clear, and e'xact description.

This invention relates to thefmetal caps of electric v light sockets oi' shells, which are commonly known as socket caps. As ordinarily constructed, these caps consist of at least three separate parts, to wt: ashell or cap projper constructed of light sheet metal; a relatively heavy hub or bushing, having a threaded bore; ancl a washer, by means of which the hub is clenched or staked to the shell. This Construction, however, has the *drawback that notwithstanding the exercise of considerable care, it will usually be found that of a given number of caps manufactured by the customary operations, some are detective owing to the looseness of the connection between 1 the hub and the shell. Then again, even if the hubs are tightly locked to the shells When the articles leave the factory, the parts are very apt to work loose *if they are* subjected to slight strains. Furthermore, withthe ordinary construction, the shell. itself is quite weak at or near the juncture with the hub or bushing, and thscauses the shell to crack When it is subjected to a comparatively slight strain.

One of the objects of my invento is to provide an improved form of socket cap n whichthe abovemrentioned defects are ehmi- *natedL Another object oi' the* invention is to furnish a simple and eflicient socket cap n which the shelland hub are integral with each other, being stamped :from a single metal blank, and wherein, nevertheless, the

l hubhas a wall of Suflicient thickness to carry a *cutl thread without buckling under the stresses to which it is subjected. Furthermore, in accordance \with my invention, the entire shell or cap proper may be made from the same piece \of metal as the hub and it i may be so designed \a as to'combine maximum lightness with maximum resistance against cracking or splitting at the zoneiof Special strain. l

To these and other ends, invention consists in the novel features and combina- Serial No. 47,522.

tions of parts to be hereinafter described and claimed.

p In the accompanying drawing,

Figure 1 s a perspective view of a socket cap constructed 'n accordance with my invention.

Fig. 2 s a vertical section of-the cap.

Fig. 8 isa detail of the blank.

F'igs. 4 to 8 inclusive show the blank at different stages in the process of manufacture; and

Fig. 9 shows one stage in a somewhat modified process of manufactura Referring particularly to Figs. 1 and 2, my improved socket cap comprises a domeshaped shell 10 of sheet or wrought metal, and a hub or bushing 11 integral therewith, at the summit of the dome and having a bore provided with interior screw threacls 12. At its free edge, periphery or rim theshell is usually provided with the flange or offset 13 which is formed as en integral part thereof. In the particular form shown, the wall of the hub ll is quite thick relati've to that of the shell and the threads 12. are cut in the wall of the hub, cr in otherwords, they are form'ed by the usual tapping operation. At and near its juncture 14; with the hub, the wall of* the shell s thicker than at the peripheral portion of the shell so as to reinforce the lineor Zone of juncture and make it thick and strong enough to resist the strains to which it is subjected. In the particular example illustrated, the cross sectional area of the shell wall is progressively increased from the rim'to the juncture with the hub. In the ordinary use of the device, the rim portion strain than the juncture between the shell and hub and it will be apparent that my Construction meets this condition in a very jeffective way. i p 4 e In making the cap I use as a blank a fiat disk 15 of brass 01' other metal, which is preferably quite thick, say, .105 gage, and of less diameter than that of the socket cap to be constructed. This blank 15 is placed in is subjected to much less means of a punch 17. The center part of .the blank is thus :graduallv curved cup or boss 18 and the cross-section of the bottom of the cup or boss is somewhat reduced as compared to the p formed with a shallow, l

initial cross-section. The blank is then transferred toa die 19, as shown in Fig. 5, and is formed by means of a punch20 coperating with said die. The die 19 is provided with a depression or recess 19 of less diameter than the blank resuiting from the operation' shown in Fig. 4, and this depression or reeess 19 has a substantially fiatbottom and an upright, substantially cylindrical side e wall. The punch 20 carries a projection 20 V characteristie that the side Wall of the boss L upwardly ,into

21 formed by this operation is thieker than any other part of the blank, that is, the cross-section area of said wall is greater than that of the flat outer or brim portion of the v hiank and greater than the cross-section of theohottom of the boss 21. The' substantiallycylindricai Wall* of the boss 21 preferably approximates the original blank in thickness. At the same time, the fiat outer portion of the blank is made very much thinner than the original biank. As the punch 20descends on the hlank resulting from the operation shown in Fig. 4,- the outer or peripheral portion of the blank is flattened out considerably by the coperating surfaces 197 20 of the che and punch, but nevertheiess, While the unconfined outer periphe'ral portion is being forced out laterally to thin the same and increase the diameter of the bla-mk; that portion of the punch surroundiw the, projection 20 forces or dispiaces the adjacent metal inward and down intothe recess 19 to form the thick Wall 21 previously mentioned To accomplish this end, the punch projeetion 20 joins the stamping surface 20 on an easy Curve or fillet and the die is shaped correspondingly. same time that the punch is forcing metal inwardly and downwai'dly into the recess 19 to form the thick wall 21, said punch is also forcing metal the wall 21 from the bottom of. the hoss. This is accomplished by designing the punchand die sothat When the 'punch is moved to its lowest position, the

.ower surface of the projeetion 20 veryforcibly the metal between it hottom of the recess 19 presses and the so as to flow or displace such meta-1 outwardly in a radial dire'ction and upwardly around the side surface of the projection 20 Itwill be understood, therefore, that the creasing or buckling.

operation shown n F ig. 5 consists of fiattem ing out and thinning the outer or peripheral part of the blank shown in F ig. 4:, thereby increasing the diamet-er of the blank; and in forming at the center portion of the blank a boss having a thick side wall, by fiowing or displacing metal outwardly and upwardiy from a zone at and near the center of the blank, and fiowing or displacing inwardly and downwardiy a certa-in amount of metal located in another zone more remoto from the center of the blank.

After the forming operation shown in Fig. 5 is compieted, the biank has its flat brim further thinned out as shown in F ig. G without, however, materially Changing the shape oir' the boss 21. This may be efi'ected by placing the blank in a die similar to the die 19 and using a punch similar to the punch 20, hut having a centering projection of less depth than the projection 20' In this operation one or more sharp quick hammerlike hlows of the punch are required. The biank shown in F ig. G is then subjected to the operation shown in Fig. 7 for the purpose of shaping the flat brim portion into a dome-shaped shell. For this purpose, the die 22 (F ig. 7) is provided with a recess 23 to receive the boss 21 and with a curved Wall 24 to give the brim portion the reqnired shape. The punch 25 comprises a plunger 26 adapted to fit the curved recess 24 of the die and carrying a centering projection 27 adapted to force the boss 21 into the recess 23, without, however, effecting any material change in the shape of said boss. The puneh 25 also comprises an independently movable member 28 which descends in advance of the plun 'er 26 and yieldingly ho]ds the peripheral part of the brim of the blank during the initiai portion of the forming operation so as to prevent the blank from crimping,

As the punch 26 is moved to its lowest position, the blank is drawn into the shape illustrated in dotted lines in Fig. 7. The biank is then removed from the die, and acted upon by another punch and die which are generally similar to these shown in Fig. 7 but are so shaped as to perfeet 'the form of the shell or dome portion 10 of the biank and form the flange 13 on the periphery thereof, as shown in Fig. 8. The drawn socket cap is then completed bv cutting out the bottom of the boss 21, (thereby Creating the hub ll), tapping the bore of the boss or hub With the threads 12, and foi-ming the customary sinal] tapped Opening 29 in the Wall of the hub.

It will be observed that the thick hub oi' the one-piece socket cap merges into the dome without any distinct'line of juncture, which is a factor of considerable importance in producing a cap of maximum strength and efiiciency. The metal of the dome is gradually increased in thickness as the diy ducea Zone of juncturebetween the hub and of the cap.

y the manner shown, by

ing to which dome which is of intermediate thickness.

The hub and dcme are preferably joined together by external and internal fillets sc that the zone of juncture is not interrupted 01' cut into bya shanp angle at the outside u y olnmg the dome and hub on or w th an external cul-ve or fillet, the Zone of uncture is not weakened and at the y same time the polishing of the cap can be accomplished more easily than heretofore.

It will be understood that intermediate the seyeral operations above described, the blank Wlll be annealed to soften the same, and permit :further stretching of the metal without breaking, and that it will be subjected tc the usual pickling operations for thoroughly cleansing the same. Furthei'mcre, it will be evident that the totalinumber* of formng 01 y drawing operations may be Varied, as called fo by conditions, and the sequence of ceitaln operations may likewise be varied without departing from the Scope of the invention. 4 broad aspect of the process of making the socket cap, it is not essential that the thick wall of the hub be formed by fiowing 01 displacing the metal both in an inward direction and an outward directionrelative to the center of the blank. e

In Fig. 9, I have illustrated another-step* of asomewhat modified method oi' lorming the cap. According to this modification, l begin With a thinner blank of, say, .050 gage, and form a substantially cylindrical boss 30 directly thereon by *means of a punch 31 and die 32. In this operation, the metal is fiowed or displaced inwardly or downwardly, and also upwardly and outwardly around the projecticn 33 on the punch, substantially as previously described. The brim porticn of the blank in this case only has to be flattened out to a slight eXtent, and therefore the pel'iphery of said brim portion is co'nfined in an upright wall 34:. Although it might appear that by starting '4 blank, the process previously with a thinner described could be somewhat shortened, the

fact is that in carrying out the peration shown n Fig 9, the comparatively la 'ge superficial area of the blank reduces to a con siderable degree the pressure per unit oi' area. The operationl is less sat1siactcry, therefore, than that first descrlbed, accordurthermore, so far as concerns the i heavy pI essure is distributedw over a small blank area in forming the blank during the initial stages.

It will be noted 'from Fig. 2, that in the particular example shown, the hub is more than twice as thick as the average thickness of the dome, and that the ueripheral fiange on the dome is not more than one-third the thickness of the main part of the hub. The hub is at any rate much thicker than the major portion of the dome and the lines ci the hub flow into those of the domc cn a curve or fillet at the exterior.

Various changes can be made in the form of the socket cap, and the method of producing same, Without departing from the invention as defined in the claims. lvlorecver, it will be obvious that the cap need not in all cases be used for the specific purposestated.

e I do not claim herein the method of making the socket cap, as such subject mattei is claimed in my application, Serial Number 7291, filed February 10, 1915, of which the present application is a division.

What I claim is: y

l. A sheet metal socket cap such as described, comprising a drawn one-piece domc *and hub, the hub being considerably thicker a thickness.

2. A sheet metal sccket cap, comprising a drawn' one-piece dome and hub, the hub being considerably thicker than the main part of the dome and gradually mergng into the latter on a fillet at the summit oi' the (leme.

3. A Socket cap cr* similar article such as described, comprising a drawn ue -piece dome and hub of sheet metal,the peripheral portion of the dome being much thinueithan the hub and gradually tapering into the latter on a fillet at the summit of the dome.

4. A drawn sheet metal one-piece socket cap, comprising a thin dome-shaped sheet metal shell and a substantally cylindncal wall at the summit of said shell merging therewith and constituting a hub, said wall being of considerably greater thickness than the shell and merging with the latter by a zone of intermediate thickness, said shell gradually decreasing in thickness from the hub to the periphery of the shell; substantially *as described.

In-witness whereof I have hereunto set my hand on the 16 daV of August, 1915.

* ALEXANDER'VV. LIMONT. 

